A Vertical Shaft Impact (VSI) crusher is a particular type of crusher that is used in the production of aggregate.
A VSI crusher includes a rotor configured to rotate within a crushing chamber at high speeds about a vertical axis. Rock material enters the rotor by an inlet port and, as the rotor spins, is ejected from the rotor via outlet ports arranged about the circumference of the rotor and is hurled against anvils placed strategically about the chamber or the rock lined shell of the crusher chamber.
The impact forces breaks down the ejected rock material into aggregate. A crusher which uses this mode of breaking down rock material is sometimes known as a “rock on rock” crusher.
Some VSI crushers create impact forces by ejecting rock material from the rotor into a cascade of rock material that falls past the outlet ports of the rotor. An example of such a crusher is described in New Zealand Patent No. 297910.
Regardless of the mode of action of the rock crusher, the rotor body and its constituent components are exposed to considerable wear and tear due to the impact of the rock material entering the rotor, and the speeds at which the rotor operates.
A conventional VSI rotor consists of a one piece steel fabricated rotor body. The body includes an inlet port, outlet ports, top plate and a base plate. The various outlet ports are formed by bolting or welding vertical members to the base plate. The rotor body is then protected by a number of wear resistant castings fixed about the rotor using a variety of methods.
To protect the top and base plates of the rotor body, top and bottom wear plates are used. The top wear plate sits over the top plate of the rotor body while the rotor body itself sits atop of the bottom wear plate.
One particular problem that affects the rotor body when it is rotating within the crushing chamber is that the perimeters of the top and base plates experience streaming wear. Fine particle streaming wear can quickly undermine the integrity of the rotor. Once the rotor begins to wear, the rate of wear accelerates. This will often require expensive repairs or replacement of the rotor.
One conventional technique used to protect the perimeters of the top and base plates is to apply a hard facing weld material to the top and bottom wear plates. Another technique is to implement hard metal rollings to the wear plates.
While these techniques do offer some protection to the perimeters of the rotor, this does not fully address the issue of fine streaming wear on the periphery of the rotor itself. Over time, the top and bottom wear plates of the rotor become worn down and will eventually require replacement.
In order to achieve the necessary maintenance and replacement of the various components of the crusher, it must be shut down. VSI crushers are significant items of machinery, processing large amounts of rock material. The rotor body is engineered accordingly.
Furthermore, the running costs of such VSI crushers can be particularly significant. Because of the expenditure associated with the purchase of crushers, and their running costs, operators tend to maximise the use of their crushers where possible.
Thus, it is undesirable to have a VSI crusher offline for extended periods of time in order to fulfill maintenance requirements such as replacing the rotor body of a crusher. The downtime of a crusher can have an impact on the throughput of the facility in which the crusher is installed. If the VSI crusher does need to be offline, then the downtime should be preferably kept to a minimum.
VSI crushers are also used in mineral material processing plants, such as mobile crushing plants, which combine the crusher with a feeding device, such as a conveyor or hopper, on a heavy vehicle. When replacing wear parts on these crushers, not only does the rotor body of the crusher have to partially disassembled but it is often necessary to remove the surrounding ancillary equipment as well. This extends the overall time required to replace the wear part.
It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.
Throughout this specification, the word “comprise”, or variations thereof such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.